Run awesome-lint on new additions

[RayBB]

Note: This PR is a repeat of #1851 since the fork or original fork was deleted. This PR address comments there.

I really appreciate this project and wanted to try to give back so it's a little easier for everyone involved.
To that end, I created this PR to automatically lint new lists when someone opens a PR to add them.

Benefits

• It will save time of maintainers by allowing them to look at the error message first
• It will provide immediate feedback to people who make a PR
• It helps people having trouble installing awesome-lint
• It is free

Risks

• As far as I know, there is no risk to users or maintainers.

What it does

• PR will lint NEW lists that are requesting to be added.
• PR will NOT lint this repo itself. If that functionality is desired it can happen in a separate PR (see Lint with awesome-lint via GitHub Actions #1794).
• PR will NOT lint the current lists in the readme.

How it does it

This PR creates a GitHub action that will do the following every time a new commit is pushed to an open PR:

1. Find the URL that is being added using git diff
2. Clone that repo
3. Run awesome-linton that repo.

The above 3 steps will ONLY run if readme.md is changed.
If readme is changed and no new URL is detected in the readme it will NOT fail with a helpful error message.
Error can be ignored if it is a cosmetic PR

Here are examples of failing commits.

Final notes

"Squash and Merge" this PR or let me know and I will squash it manually.

Feel free to edit this any way you see fit or ask me to make the edits. 👍
If there are any questions on how this works drop them here and I'll try my best to answer.

Again, thanks so much for all the hard work the maintainers put into this repo! 👏

[RayBB]

@sindresorhus have I addressed your concerns?

[sindresorhus]

Thanks :)

[sindresorhus]

@RayBB The scripts throws an error: https://github.com/sindresorhus/awesome/pull/1990/checks?check_run_id=2468601026

[Tolito20]

Galván Gómez